Process of treating incandescent-lamp filaments.



v lamp are exhausted with mercury pumps which 's'ists in burning it fora certain period at its normal voltage and during th s operation vapor. and the filament.

' UNITED strnrns Parana?" orrronf noiznnr H. nnnnnnson, or vnas'r cannon, N W JERSEY, nssrcnon 'ro wns'rmenonsn LAMP com-AN A conronA'rIoN-or PENNSYLVANIA.

No Drawing.

To all whomit'may concern: i

son, a' citizen of the United States, and a resident of East Orange, in the "county of Essex and State of New Jersey, have invented a new and useful Improvement in:

Processes of Treating lncandesccntsLamp Filaments, of which the following is a specification. f'

My invention relates to certain improvements in the manufacture of incandescent electric lamps, the object being to produce incandescent lamps having filaments of higher efficiency and greater durability than obtamed by the usual processes;

The invention is particularly applicable? to filaments composed of or containing tung sten.

In the manufacture of incandescent'lamp'st consisting of tungsten or similar-materials, the ordinary process consists in squirtingthe filament from-a paste and sintermg the metallic particles together by heating the filament to a temperature about the equivalent of the temperature at which the filament is to be run in the finished lamp. The filament thus prepared is then introduced into the bulband the latter is" exhausted of air-,the filament being heated during this operation to approximately the same or a little higher than the temperature it Will have while burning in the finished lamp. This procedure is followed when the lamps give a yer-y high vacuum. \Vhen the exhaust process is conducted by means of oil vacuum pumps which give a lower vacuum, it has been customary to' follow the same )IGCGClUI'B as in the manufacture o'f'carbon lamps,- namely to introduce a small amount of phosphorus yapor into the bulb just be fore the lamp is sealed off from the pump for the purpose of obtaining a higher vacuum. duce any reaction between the phosphorus The completed filament isat best but imoerfectly smtered together and represents merely a mass of metallic particles superficially welded and sintered together and after the lamp is exhausted itisnecessary Specification of Letters Patent. Application filedpecember 5,1910. Serial No. 595,631. 1

- ably prepared emu No attempt is made, however, to prornocnss' or rnmrmo moAu-nnsonn'r-tnmr'rumnnrs-' Y the filament-under' oes a further sinte'ring. .Be it known that I, 'Ronnn'r HENDER- (Examined under t e microscope such filament does not present a smooth surface but has-a rather rough and pitted appearance.

. It is well understood in the manufacture of lamps that a filament with a. smooth surface superior to one with a rough surface as far as its luminous efliciency and light emissivity is concerned, It is desirable, therefore, that means he found for'producing the tungsten or like filament .with a much more smooth exterior than obtained by processes heretofore proposed. I find Patented Feb. 3,1914.

that when the filament is heated to a very hi ghtemperature in a high vacuum, its. surface ISSOIHGWhil-l? improved, but if at that lu'gh temperature it is surrounded with an atmosphere of gas or vapor' such for instance as phosphorus, a markedfimprovement is obtained and a filament is produced which, under the. microscope, appears much more smooth and brilliant. This smoothness of surface may be due to a tiuxing of the metallic particles at the surface of the filament as their appearance is as though they were caused to flow together under the combinedaction of the high tempe'rature'and the gas or "vapor. This may possibly-be due to the intermediate formation of an alloy or compound of the metallic particles and the gas, at the surface of the filament, which alloy or compound is, immediately decomposed. I do not, however, desire to'be understood as giving this explanation as necessarily the correct one, butit is advanced as being avprobable explanation. The filament ma be dipped into a, suitlsion of the reacting element or a suitable compound thereof, orthe reacting gas'may be obtained by directly vaporizm sufiicient quantity of the element or o a suitable compound thereof.

' Iprefer to carry out this process in conjunction with the ordinary process of exhausting the lamp of air. Thus, for instance, 'after the lamp has undergone the regular process of exhaust and would ordi- -narily be considered finished, I raise the filament to a very high temperature for a con 'siderable time, say from three to ten minutes, by means of applying to it a voltage very much 1n excess of its normal volt-age.

Toward the end of this 0 oration and while the lampis still at this high temperature, I

too

allow a small quantity of'a gas or vapor such as phosphorus vapor to enter into the lamp. This I usually accomplish by the previous introduction of a small quantity of phosphorus into the tube which serves for exv haustingthe lamp, and I vaporize the phosphorus.

phorus b heating it by means of a small torch. 'Bhe phosphorus then seems to act upon the material in the way above described and to produce a smooth highly efficient surface. The process .may be repeated in some in stances for obtaining a more thorough treatment, but'usually this is not necessary.

I do not Wish to confine myself to the specific material phosphorus as I find in practice that various other materials, such for instance as arsenic, and sulfur, and the like may be employed, but thus far I have obtained the best results by the use ofphosvI find that filaments 'thus made do not have to be afterward aged as the texture and structure of the filaments seem to be much more permanent than when made b the usual processes.

I claim as my invention:

1. The process of manufacturing metallic filaments for incandescent electric lamps, which consists in heating the filaments to a' temperature in excess of their normal operating temperature in a vessel exhausted of air, and simultaneously acting upon the same by a gas or vapor serving to reduce the surface of the filament to a compact smooth condition. 4

2. The process of manufacturing metallic filaments for incandescent I lamps, which consists in heatin the filaments to a temperature materially igh'er than the operating temperature thereof in an atmosphere of phosphorus for a sufiicientlength of time to change its surface characteristics.

3. The process of manufacturing filaments for incandescent lamps, which consists in heating the filaments to a temperature materially higher than the operatingtemperature thereof in an atmosphere of phosphorus for aperiod materially longer than is customary in the process of exhausting.

4. The process of treating a metallic incandescent lamp filament which consists in heating the same w-hile evacuating the lamp in the presence of an atmosphere of phosphorus to a temperature materially in excess of its temperature when in normal use for a sulficient length of time to change its surface characteristics. 1

5. The process of treating a metallic in-' candescent lamp filament, which consists in applying to it while it is located in a vacuum a voltage materially in excess of that/applied to it in normal use and subjecting ROBERT H. HENDERSON.

Witnesses:

GEORGE P. SoHoLL,

CHARLES E. 

